NEW: save a 2D matrix to a .txt file
NEW: save a 2D matrix to a .txt file

Former-commit-id: 302ba21a7e871adc8b25475017d079744d11a001 [formerly 93a35fbe54ec8e9ba1f4db8bc679f752f9ab1772]
Former-commit-id: 069ffa96bb267fdb70b9c6cbb3990a0e96397b58
Former-commit-id: 31e8d58fb331b5addb76810d33493a0e21423920
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox